The present invention relates to apparatus for thermally propagating a quench in a multicoil magnet from the initially quenched coil to all the other coils.
A superconducting magnet having several coils can, during operation, have a portion of one of the coils change from the superconducting state to the normal state due to a temperature rise resulting from local heating caused by wire movement or insufficient cooling. A quench of the coil occurs if the entire coil transitions to the normal state. Quenching can also occur during powering up of the magnet due to changing field strengths caused by increasing currents. Loss of the superconducting state at one location in a coil where the superconductive wire or tape presents resistance to the current flow usually is followed by a quench of the entire coil. During the quench, all the magnetic energy stored in the circulating currents of the magnet are then dissipated as thermal energy.
A quench is a fast transient and high energy phenomenon which can cause permanent damage to superconductive coils due to the resultant thermal and electrical stresses. Every superconducting magnet needs to be designed so that it can withstand a quench without causing damage to the magnet wiring, allowing the magnet to be repowered and used again.
In a series connected multicoil magnet system, if no active or passive protection system is provided, all of the energy of the magnet can be dissipated in the quenched coil resulting in an excessive temperature rise, damaging the quenched coil. It is desirable to distribute the stored magnetic energy among all the coils by initiating a quench in the other coils when a quench is detected in one coil. Quench propagation is presently achieved by electrical and magnetic coupling, designed so that the rising resistance of the quenching coil induces heating and/or increases the current in the other coils, which eventually initiates a quench in those coils.
It is an object of the present invention to provide apparatus for propagating a quench from one quenching coil to other nonquenched coils by heat conduction without relying on electrical or magnetic coupling.